Studies are projected on the further characterization of the two types of Ia like B cell alloantigens and their significance in human transplantation. Investigations will continue on V region antigens defined from myeloma proteins and their possible relationship to T cell receptors for antigen. Specific antisera to V region subgroups of the H chains will be utilized in studying T cell membrane receptors. BIBLIOGRAPHIC REFERENCES: Kunkel, H.G., Joslin, F. and Hurley, J.: Blocking of certain antigenic sites in the F(ab) region by combination of univalent fragments of Rh antibodies with red cell antigens. J. Immunol. 116: 1532, 1976. Natvig, J.B., Kunkel, H.G., Rosenfield, R.E., Dalton, J.F. and Kochwa, S. Idiotypic specificities of anti-Rh antibodies. J. Immunol. 116: 1536, 1976.